[R] subsetting a dataframe

[Prof Brian Ripley]

On Tue, 4 Mar 2008, John Sorkin wrote:

> windows XP
> R 2.6.0
>
> I am having problems deleting a row from a data frame. I create my dataframe by subsetting a larger dataframe:
>
> ShortLavin<-Lavin[Lavin[,"Site"]=="PP" | Lavin[,"Site"]=="CC" | Lavin[,"Site"]=="FH",]
>
> I then perform a glm using the data frame and plot the results.
>
> fit1poisson<-glm(NumUniqOpPt~Seq+Site,family=poisson(link = "log"),data=ShortLavin,offset=log(NumUniqPt))
> plot(fit1poisson)
>
> On the plots I see a point labeled as 127 that is an extreme value. I want to re-run the glm excluding the extreme observation. I have tried several methods to exclude the observation (shown below), none have worked.
>
> Minus127<-ShortLavin[-127,]
> Minus127<-ShortLavin[-"127",]
> Minus127<-ShortLavin[-c(127),]
> Minus127<-ShortLavin[-c("127"),]
>
> None of these worked. Suggestions on how I can remove observation 127 would be appreciated

Assuming this is row name "127" derived from row 127 of  the original 
dataset,

Minus127 <- ShortLavin[-match("127", row.names(ShortLavin)), ]


>
> Thank you,
> John
>
> John Sorkin M.D., Ph.D.
> Chief, Biostatistics and Informatics
> University of Maryland School of Medicine Division of Gerontology
> Baltimore VA Medical Center
> 10 North Greene Street
> GRECC (BT/18/GR)
> Baltimore, MD 21201-1524
> (Phone) 410-605-7119
> (Fax) 410-605-7913 (Please call phone number above prior to faxing)

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595